This invention relates generally to devices used to adjustably secure tractor wheels to the tractor axle and, more particularly, concerns wedge lock assemblies which are slidably adjustable axially in their unlocked condition.
In today's agricultural industry the tractors used must perform a wide variety of operations, each of which require a particular separation between the drive wheels of the tractor. The existing configurations which attempt to adjustably secure the tractor wheel to the axle include the use of wedge arrangements to provide the desired locking effect. Although these configurations produce an adjustably secured wheel assembly, they suffer from several problems which our invention overcomes with its nonobvious and novel combination of elements.
One of the difficulties with the existing wedge arrangements lies in the magnitude of the release torque required to unlock the wheels after they have been in use. This torque must be kept at a level that permits changing the wheel spacing in the field as well as in maintenance areas. When the existing arrangements have been locked and have transmitted force to the wheels, the wedges and hubs become fused together through the process of cold welding which is the plastic deformation of materials due to excessive loading. As a result of this fusing the unlocking torque required for the existing arrangements becomes unacceptably high.
The second difficulty arising from the existing arrangements also relates to the unlocking torque required after use in the field which distorts the shape of the hub. The distortion is caused by the arrangement's hub material being softer than the wedge material thereby producing controlled elastic deformation during the extended periods of force transmission. This deformation increases the unlocked torque required since the wedges were designed to engage a spherical hub and upon removal they are engaged with an eliptical hub.
The third difficulty with the existing wedge arrangements manifests itself in the failure of the arrangement caused by erosion of the wedge elements. The erosion occurs during the transmission of forces from the tractor axle to the tractor wheel when the non-transmitting wedges lose contact with the axle and when the table leg geometry of the wedges leaves the short leg free. This lack of contact permits the wedges to vibrate and contact the hub and axle under impact loading conditions which erode the wedge at a variety of locations. The arrangement loses its lockability when the erosion interferes with the mating of the elements of the arrangement.
Accordingly, it is the primary aim of the invention to provide a wedge lock wheel assembly which is capable of varying the tractor wheel tread separation within both the maintenance areas and in the field while minimizing the costs and complexity of the assembly.
Moreover, it is object of the invention to provide a wedge lock assembly that has a positive disengaging of the assembly without adversely effecting the torque necessary for disengagement.
With more particularity, it is an object of the invention to provide a wedge lock assembly of the stated character that also minimizes the jamming effect of the wheel hub distortion without decreasing the position control or the forced transmission capabilities of the assembly.
Finally, it is an object of the invention to provide a wedge lock wheel assembly that transmits force without producing cold welding or erosion of the locking elements.